Synchronizing system



Oct 10, 1933. M. B. LONG 1,930,245

SYNCHRONIZING SYSTEM Original Filed Dec. 18 1923 2 Shets-Sheet 1 IN VEN727/? M & LONG ATTORNEY Oct. 10, 1933. M. B. LONG SYNCHRONIZING SYSTEM 2Sheets-Sheet I 2 Original Filed Dec. 18 1923 Qmk ATTORNEY Patented one10, 1933 1,930,246 SYNGHBONIZING SYSTEM MaurlceB. Long, Glen Ridge, N.1., assignor to Western Electric Company, Incorporated, New

York, N. Y., a cof'poration of New York Original application "December18, 1923, Serial Divided and this application Febmar! 18, 1929, SerialNo. 340,903, and in Germany-Angust 23, 1924 Claims. (01. 172-293) Thisinvention relates to synchronizing and more particularly to thesynchronization of the movable elements employed at different stations 5respectively of a carrier picture transmission system.

This invention is a division of a copending application, Serial No.681,347, filed December 18, 1923, which matured into Patent 1,706,032,March 19, 1929. In accordance with this invention synchronization ofmovable elements is accomplished in a novel, simple and effectivemanner.

In a preferred embodiment of the invention, the

elements to be moved in synchronism are under,

the control of a carrier current of a frequency different from anothercarrier current transmitted over the same line between the primarymechanisms at the two stations, such as signaling apparatus. Theelements to be synchronously operated are driven by two separate sourcesof current and the synchronizing carrier current, which is suitable fortransmission over the line or other transmission medium connecting thestations at a ing current from a photo-electric cell for transer is usedfor producing synchronized movement of the scanning and reproducingelements. 'The first mentioned waves are also used to effect the releaseof the scanning and reproducing elements simultaneously -to commence thetransmission process. These elements are driven by phonic wheels, eachof which is controlled by a tuning fork. At the sending station, thefork causes the transmission of impulses of synchronizing waves, whileat the reproducing station the fork is actually driven by detectedcurrent so that it vibrates in synchronism with the fork at the sendingstation.

Fig. 1 shows schematically the apparatus at the sending station and itsconnection to the transmission circuit.

Fig. 2 shows schematically the apparatus located at the reproducingstation and likewise its connection to the transmission circuit.

I The complete system is shown by placing Figs. 1 and 2 side by side,with Fig. 2 on the right hand side.

Referring now to the drawings, a sending drum 5 is driven by a phonicwheel 6 by means of a shaft shown atically by dotted lines. The

mitting the picture characteristics, while the othcoupling between thedrum 5 and the phonic wheel 6 is through a friction clutch 7. The phonicwheel 6 is itself driven by tuning fork SF in well known manner. Anelectrondischarge oscillator supplies carrier waveswhich are amplifiedby electron discharge amplifier SSA and transmitted through circuit 8and low-pass filter SSF to the line L for transmission to thereproducing station of Fig. 2. An extra contact 9 on tuning fork 81'short circuits circuit 8 periodically at the frequency of vibration ofthe tuning fork SF. At thereproducing station of Fig. 2, thesesynchronizing waves are transmitted through low pass filter RSF,amplified in the twostage electron dischargeamplifier RSA. and detectedby the electron discharge detector RSD to drive the reproducing tuningfork RF by means of impulses of current in driving magnet 10. The

A photoelectric cell 15 located inside of send- 1 ing drum 5 isconnected to the input circuit 16 of a two-stage electron dischargeamplifier PCA.

Light from a lamp 17 is focused by means of lens 18 upon the surface ofsending drum 5, which is transparent. The light ray also passes throughan aperture in an opaque shield 45'. On the surface of the drum 5, atransparency of the picture to be transmitted is secured and the lightpassin through this transparency of the picture causes a varying currentfrom the battery 19 to fiow through the photoelectric cell 15 and to beimpressed'upon the input circuit 16 of amplifier Waves from theoscillator PO may be impressed upon the amplifier MCA by. either one oftwo paths. One path extends from the output circuit switch 47, the lowerwinding of relay 2'? is effective to close contact 26. When the switch4'7 is closed, the upper winding of relay 2'? is effective to closecontact 29. Under this same condition, armature 49 of relay 48 isattracted and locks sending drum 5 against rotation.

At the reproducing station, picture carrier waves from the oscillator P0are transmitted by high pass filter RPF, amplified by amplifier EPA, andimpressed upon reproducing demodulator RPD. Connected in the outputcircuit of demodulator RPD is a battery 30, the movable wires of lightvalve 31, and winding 32 of relay 33.

The opening between the movable wires of light valve 31 controls theamount of light from lamp 43 which affects a sensitive film secured toreproducing drum 12. The light from lamp 43 is focused first upon themovable wires of light valve 31 and then upon the surface of the drum bylenses as shown. The light is further concentrated by passing through anaperture in the opaque shield 44.

The armature of relay 33 is held in the position shown with contact 34closed by the current flowing in winding 32-when carrier waves areimpressed upon the input circuit of demodulator RPD. When such waves arenot being received, the armature of relay 33 is moved into a positionclosing contact 35 by current in winding 36 from battery 37.

The closure of switch 38 completes a circuit for relay 39 throughbattery 40. Current in relay 39 attracts its armature 41 to lock drum l2and prevent its rotation. Another circuit for relay 39 through battery40 is closed when contact 34 of relay 33 is closed, even 'though theswitch 38 is opened. It is to be noted that the closure of switch 38forms a short circuit about the contact 34. The circuit completed by theclosure of switch 42 and contact 35 forms a short circuit about thewinding 32 of relay 33.

The oscillators SO and P0 are of well known type and are identicalexcept for the different constants of the circuit required to producecarrier waves of different frequencies. Each one has a three-electrodeelectron discharge device having an input circuit coupled to the outputcircuit by transformer 60. The frequency is determined by the tunedcircuit consisting of the left hand winding of transformer and condenser61. Connected in series with the feed back portion of the output circuitis a high resistance 62. The output waves for transmission purposes aretransmitted through potentiometer 63. In the case of oscillator PO, itis preferable to have the potentiometer variable in such a manner thatthe working circuit cannot be connected across the entire resistance ofthe potentiometer.

The amplifiers SSA, PCA, MCA, RSA, and EPA each include three-electrodeelectron discharge devices and are so designed as to properly transmitand amplify the waves impressed thereon.

Similarly, the detector BSD and demodulator RPD employ three-electrodeelectron discharge devices. A relatively large grid polarizing battery64 is used in each case to accomplish detection and demodulation. In thedemodulator RPD, a tuned circuit, consisting of an inductance coil 65and a condenser 66 is provided to prevent current of carrier frequencyfrom being impressed upon the light valve 31. Circuit 65, 66 is tuned tothe frequency of carrier waves produced by oscillator P0.

The filters are designed according to the prinrcaopae ciples set forthin Campbell Patent No. 1,227,113, May 22, 1917.

Method of operation The method of operation will now be described.

The drums 5 and 12 are set at the starting position in any suitablemanner. The transparency of the picture is placed on drum 5 and asensitive recording blank is placed on drum 12. Switch 47 is closed,which looks drum 5 through the energization of relay 48 and closescontact 29 of relay 27. Switch 38 is closed, which locks drum 12 by theenergization of relay 39. Switch 42 is kept open. I

The circuits of the electron discharge devices are then energized.Synchronizing carrier waves from the oscillator SO are transmittedthrough amplifier SSA, circuit 8, low pass filter SSF, line L, low passfilter RSF, amplifier RSA, to detector BSD. Picture carrier waves aresupplied by oscillator PO and transmitted through transformer 21,Contact 29 of relay 27, amplifier MCA, high pass filter SPF, line L,high pass filter RPF, amplifier EPA, to demodulator RPD. Demodulatedcurrent flows in light valve 31 and winding 10d 32 of relay 33 to closecontact 34.'

Tuning fork SF is then set in vibration and phonic wheel 6 is started.This tends to rotate sending drum 5 through friction clutch 7, but drum5 is locked by the armature 49 of relay 48. At contact 9 of fork SF, thetrain of carrier waves from oscillator S0 is periodically interrupted atcircuit 8, so that trains of waves are transmitted to the line L. Thesewaves in detector RSD cause impulses of current in driving magnet 10 todrive tuning fork RF in synchronism with tuning fork SF. Phonic wheel 11is started and tends to drive drum 12 through friction clutch 13, but isprevented from doing so by the armature 41 of relay 39.

Switch 23 is now closed, switch 42 is closed and switch 38 is opened.Picture carrier waves from oscillator P0 are impressed upon the inputcircuit of modulator PM, the output circuit of which is still open,however, at contact 26. Drum 12 is still held in locked position by theenergization of relay 39 through a circuit including contact 34 of relay33.

Everything is in readiness now to start the transmission of the picture.Phonic wheels 6 and 11 are rotating synchronously. Drums 5 and 12 arelocked against rotation. Light valve 31 is energized by demodulatedpicture carrier waves.

To start the actual transmission, switch 4''! is opened and kept openduring the transmission process. The opening of switch 47 deenergizesrelay 48, which unlocks sending drum 5. The upper winding of relay 27 isdeenergized so that contact 26 is closed'and the output circuit 25 ofpicture modulator PM is connected to the input circuit of amplifier MCA.During the time that the armature of relay 27 is moving from contact 29to contact 26, the picture carrier waves are interrupted. Suchinterruption allows the armature of relay 33 to move from contact 34 tocontact 35 because of the deenergization of winding 32. This unlocksreproducing drum 12 by the deenergization of relay 39. The closure ofcontact 35 places a short circuit around winding 32 so that thesubsequent receipt of carrier current by demodulator RPD upon theclosure of contact 26 cannot again energize winding 32 to lock drum 12.

The varying tone values of the transparency of the picture cause varyingcurrents through the photoelectric cell 15. Carrier waves fromoscillllll later P are modulated by these varying currents afteramplification in amplifier PCA, and trans mitted to the demodulator RFD.Corresponding varying currents in the output circuit of demodulator REDcause movement of the wires of light valve 31 so that the lightimpressed upon the reproducing blank is varied in accordance with thelight transmitted through the trans=-- parency of the picture at thesending drum 5.

At the conclusion of the process, switch d? is closed to locktransmitting drum 5. The attendant at the reproducing, station observingthat the movement oi the light valve has ceased, can either open switch42 or close switch 3% or truth to lock the reproducing drum l2.

The drums can then be returned to their starting position in preparationfor the transmission oi another picture.

Various modifications oi the specific embodiment of the invention, whichhas been described, cm be made without departing from the scope of theinvention as defined in the appended claims.

' What is claimed is:

Q current, whereby synchronism of vibration is vibration of the secondfork in synchronisrn with the iii-st fork operated by current derivedfrom said varying transmitted waves.

2. In a synchronizing system, two phonic wheels,

two tuningforhs for driving saidwheels at a speed proportional to therates of vibration of said forlrs, a source of carrier waves, a circuitover which said carrier waves are transmitted, means to interrupt saidcarrier waves at a rate proportional to the vibration of one of saidforks, and means under the control of said interrupted waves for drivingsaid second fork in synchronism with said first fork. a

3. In a synchronizing system, two phonic wheels, two tuning forks fordriving said wheels at a speed proportional to the rates of vibration ofsaid forks, an electron discharge oscillator supplying carrier waves, acircuit suitable for transmitting said waves, means to short-circuitsaid circuit periodically at a rate proportional to the vibration of oneof said forks, an electron discharge detector connected to said circuitfor providing impulses of current in accordance with said inter ruptedtrain of carrier waves, and means to drive the other of said two forksby said i'm pulscs of maintained between said two forks.

4. In a synchronlzingsystem, two mechanically independent elements to bemoved in synchronism,

. means for starting the movement of said elements simultaneously, meansfor operating each of said elements, and means comprising an alternatingcurrent varied at selected intervals according to the movementof one ofsaid elements when operated to hold the other element in synchronism.

5. In a synchronizing system two mechanically independent elements to bemoved in synchronism, means for restraining the movement of saidelements to hold them in a predetermined position, means for releasingsaid restraining means to in,- itiate the movement of said elementssimultaneously, means for operating each of said elements, and meanscomprising an alternating current varied at selected intervals accordingto the movement of one of said elements when operated to hold the otherelement in synchronism.

6.121 a synchronizing system two movable elements'located at differentstations respectively, separate sources of current for driving saidelements, ,a transmission channel connecting said stations, two sourcesof carrier current at one of said stations, means for starting themovement of the element at one of said stations and for simultaneouslymodulating the carrier current from one of said sources to control thestarting of the movable element at the other station, and means formodulating the carrier current from the other of said sources formaintaining said movable ele merits in synchronism.

7. A transmission system comprising transmitting apparatus at onestation, receiving apparatus at another station under control ofsaidtransmitting apparatus, means for generating and transmittingalternating carrier current for eifecting said control, moving elementsat said stations forming parts of said transmitting and receivingapparatus respectively, and means for generating and transmitting forshort intervals at a time over the same medium as said first carriercurrent a separate carrier current oi different frequency formaintaining said movin elements in synchronismfl 8. A control circuitinterconnecting two statill tions, a motor driving mechanism at eachstation, vibrating driving forks for each of said motors, meansassociated with said control.circuit'at each of said stations andcontrolled by the frequency of vibration of the fork at one station forcontrolling the frequency of vibration of the fork at the-other station,starting mechanism for each of said motor driving mechanisms, and meansassociated with said control circuit at one of said stations forsimultaneously operating said starting mechanisms.

9. A control circuit interconnecting two stations, a motor drivingmechanism at each station, vibrating driving forks for each of saidmotors, means associated with said control circuit at each of saidstations and controlled by the frequncy of vibration of the fork at onestation for controlling the frequency of vibration of the fork at theother station, clutch mechanisms for each of said motor drivingmechanisms, relay means associated with said control circuit at one ofsaid stations tuned torespond to oscillations of a desired frequency, anoperating circuit for the clutch mechanism at said station controlled bysaid relay means, and means at the other of said stations for applyingto said control circuit oscillations of a desired frequency to operatesaid relay means and for operating the clutch mechanism at said lastmentioned station.

10. The method of synchronizing two movable devices at widely separatedplaces which comprises operating, the 'two devices, generating analternating current at one of said places indeing said alternatingcurrent 'according to the frequency of operation of the device at saidfirst Jill) pendent of the movement of the devices, varyno

